@sirspuddington – I’m not 100% on which is the fastest or best one to be honest! Out of all of them, maybe one of the Audi R8’s or Group C cars might be the best or most fun to drive. The Peugeot 908s are good as well, and are more easily obtainable, since they are premium. All of the cars listed (except possibly the Audi R10) go to 700PP, which is the limit, of course.
If you need any more guidance then there are some threads on GTPlanet that can point you in the right direction.
So can you make it for 8pm on Monday? :) The track is Grand Valley Speedway.